Signal-seeking, power-driven mast for use in laser beam controls and surveying systems

ABSTRACT

This invention relates to the construction of a power-driven extensible mast for mounting a photocell unit which is utilized to detect a laser beam which is periodically swept over a working area at a known elevation. Suitable circuits are provided between the photocell unit carried by the extensible mast and a motor unit which effects the raising and lowering of the mast to automatically maintain the mast at a height corresponding to exact vertical alignment with the photocell unit with the laser beam. Another feature of the invention is the provision of automatic limit switch means which function to reverse the direction of the driving motor when the mast reaches either the top or bottom extremity of its vertical movement.

United States Patent n 1" Teach July 23, 1974 SIGNAL-SEEKING, POWER-DRIVEN MAST Primary ExaminerRobert l(. Schaefer FOR USE IN LASER BEAM CONTROLS AND Assistant Examiner-W; E. Duncanson, Jr. SURVEYING SYSTEMS Att0rney,-Agent, 0r Firm-W. A. Schaich [75] Inventor: Ted L. Teach, Springfield, Ohio ['73] Assignee: LauerplaneCorpontiomDaytonf [57] ABSHMCT Ohio A v This invention relates to the construction of a powerdriven extensible must for mounting a photocell unit M' whic' hisutihzed' todetectalaserbeamwhichispen [2! I I Appl, No-.: 358,881 odicaliy swept over a' working area at a known eievm tion. Suitable circuits are provided between the photocell unit carried by the extensible mast and a motor 3l8/266d035h87gi which effects the-raising and lowcring of the mast [58] Field of 267 468 to automatically maintain the mast at a height correv sponding to exact vertical alignment with the photo- References Cited cell unit with the laser beam. UNITED STATES PATENTS Another feature of the invention is the provision of 3 002 598 10/196] H Y 38 468 x automatic limit switch means which function to. 1 2, 9/1967 f 84266 x reverse the'direction of the driving motor when the 7y r mast reaches either the top or bottom extremity of its vertical movement.

3 Claims, 6 Drawing Figures 23b 2 23d 23C--\ 23 K- ZBi )D 7 23 L 20 W F lZb 14'; A ET" lab I 12 I A I I I20. I

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\Gb Us H 1 SIGNAL-SEEKING, POWER-DRIVEN MAST USE IN LASER BEAM CONTROLS AND SURVEYING SYSTEMS 1 FOR I BACKGRO UNDOF THE INVENTION In US. Pat. No. 3,588,249, issued to Rober t I-I. Stu- I debaker, there is disclosed and claimed apparatus for generating a laser beam reference plane by periodically sweeping a laser'beam over a working area. In US. Pat. No. 3,494,426, also issued to Robert H. Studebaker, there is disclosed a control apparatus for graders and similar earthworkingirnplements which employs a laser beam responsive photocell unit mounted on a vertical tem disclosed and claimed by said Studebaker patents have become apparent, it has become equally apparentv that there is a need for a'power-driven, signal-seeking,

extensible mast for mountinga laser beam responsive working height of. the blade of the grader.

'tocell on top of said mast.

FIG. -1 is a schematic,side elevational view of a laser beam transmitter and 'a vehicle carrying a power-driven variable-height mast and a laser beam responsive pho- FIG. 2 is an elevational view partly in section of the vertically adjustable mast and photocell unit.

FIG. 3 isan enlarged scale, partial sectional view taken on the plane 3-3 of FIG. 2.

FIG. 4 is an elevational view of the lower portions of the mast of FIG. 2 with positions in section.

FIG. 5 is an enlarged scale perspective view of the mast limit switch mechanism.

FIG. 6 is a circuit diagram of the mast height control system.

Referring'to FIG. 1, there is schematically illustrated a basic surveying or control system utilizing the principhotocell unit, which mast maybe mounted on any vehicle traversing uneven terrain andthe effective'height of such mastcan be automatically controlled, through signals generated by the photocell unit, to maintain the ples of laser beam control disclosed and claimed mus. Pat. No. 3,588,249. A laser beam transmitter 1, of the type disclosed in said patent, is mounted at a point on the terrain where the elevation is known and adjusted to periodically sweep. a laser beam L over the adjacent terrain. The position of the moving laser beam is adjusted to lie exactly in a horizontal plane which, obviously, will be at a known elevation. The laser beam L is then detected by equipmentcarried by a vehicle 2 moving-over the terrain. Vehicle 2 may, as shown in this application, constitute a Jeep andbe utilized for,

surveying purposes.

A signal-seeking, automatically vertically adjustable mast 1 0 is carried by the vehicle 2,-and on the topof r the mast 10 a photocell unit 20 is mounted which is rephotocell unit in exact vertical alignment with the laser beam. The resulting vertical movements of the mast may be utilized tocontrol the effective working height of an earthmoving instrument, such as the blade of a scraper or bulldozen or, as disclosed and claimed in my copending application Ser. No. 358,835, filed concurrently herewith, such vertical movements of the-powerdriven, signal-seeking'mast may be recorded as a function of the distance traversed by the vehicle to automatically provide an elevational contour of the terrain traversed by the vehicle. v

Accordingly, it is an object of this invention. to provide an improved power-driven, extensible mast structure for mounting a laser beam responsive photocell unit.

A particular object of this invention is to provide a power-driven, extensible mast for mounting a laser beam responsive photocell unit, wherein the vertical movements of the mast may be controlled by signals generated by the photocell unit to maintain the photocell unit in exact vertical alignment with a laser beam that is periodically swept over a working area at a known elevation.

I Still another particular-object of this invention is to provide an improved, power-driven, extensible mast construction, including automatic limit stops and a secondary. indicating shaft which is rotated in linear relationship with the vertical movements of the mast to provide a mechanical signal of such movements which may be employed to operate a recording or control device.

. Other objects and advantages of this invention will become apparent from the following description, taken in conjunction with the annexed sheets of drawings on which sponsive to the laserbeam L. Signals generated byv the photocell units20 are'then utilized to control the effective height of the adjustable mast 10 to keep the center of the photocell unit 20 inexact vertical alignment with the reference plane definedby the laser beam-L.

The resulting vertical movement of the adjustable mast 10 may then be converted to a horizontal or mechanical signal which, if recorded, automatically provides a plot of the elevation of the terrain'traversed by the vehicle 2. I

Referring now to FIG. 2, the vertically adjustable mast 10 comprises an inverted cup-shaped mounting base 11 having a top horizontal wall 11a and a depend ing peripheral flange 1 lb defining a power transmission chamber 1 1c. The bottom of chamber 1 1 0 may be conveniently closed by a mounting plate 11d which can be utilized to mount the mast on the vehicle 2. An upstanding cylindrical wall lle is integrally formed on the base 1 1 and a tubular housing 1 2 of substantial axial extent is anchored in said cylindrical wall.

A tubular mast 13 is then'slidably mounted in the housing 12. The housing l2 is provided with a plurality thereto by screws 13b and the spaces between said an-. nular segments define grooves which slidably cooperate with the guide ribs 12a provided on housing 12.

Thus mast 13 may be slidably moved upwardly or downwardly relative to housing 12 but cannot be rotated.

A. circular nut 13d (FIG. 3) is then provided in the bottom end of mast l3 and may be secured therein by the same bolts 13b as are utilized to secure the annular segments 13a to the mast 13.

A mast height adjusting screw 14 is provided comprising an elongated rod which is threaded over the major portion of its length but has a cylindrical section 140 adjacent its bottom portion which is journalled in a bearing 11 f provided in the horizontal wall 11a of the base 11. The extreme lower end 14b of the screw 14 extends into transmission chamber 11c and mounts a limit switch mechanism 15 which will be hereinafter described in detail.

A reversible driving motor 16 is mounted on the horizontal wall 11a of base 11 and has its output shaft 16a projecting downwardly into the transmission chamber 116. While in the specific example illustrated in the drawings, motor 16 is shown as being electrical, it will be obvious to those skilled in the art that an air or hydraulic motor could be equally utilized, depending upon the power available on theparticular vehicle 2 on which the mast is mounted.

A' frictional driving pinion 16b is secured to the motor shaft l6a and frictionally engages the periphery of a substantially larger friction gear 140 which is mounted on and keyed to the lower portion 14b of the mast type adjusting screw 14. it is therefore apparent that, depending upon the direction of rotation of the motor 16, the-effective height of mast l3, and hence theeffective height of photocell unit carriedby the top of such mast, may be raised or lowered.

In order to prevent the raising or lowering movements of the mast 13 from exceeding the extremities of the adjusting screw 13, a limit switch mechanism 15 is provided.(FIG. 5) comprising a horizontal plate 15a,

on the bottom of which is mounteda bracket 15f. A vertical stub shaft 15b is journalled in bracket 15f and is threadably secured to the bottom end 14b of the adjusting screw l4. A worm-type drive pinion 14d is secured to stub shaft 15b and rotates with screw 14, but plate 15a is prevented from rotating by a projection 150 which is engaged by a U-shaped bracket 11g secured to base 11 by a bolt 11h. A limit switch actuating rod 17 is journalled in horizontal relationship below the bottom surface of plate 154 by brackets 15d and lSe and rod 17 has threaded end portions 1.7a and 17b respectively engaging internally threaded switch actuatingnutblocks, 17c and 17d. The actuating rod 17 is rotated in proportion to the vertical movements of the mast 13 through a speed reduction gear train comprising an intermediate shaft 17e also journalled between brackets 15d and 15f in horizontal relationship below the bottom of plate 15a and carrying on one end a pinion ll7f which is engaged by the drive worm 14d. The other end of intermediate shaft 17e carries a drive pinion 173 which meshes with a corresponding pinion 17h mounted on the end of the limit switch actuating rod 17.

A pair of limit switches 18a and 18b are mounted in side-by-side relationship adjacent to the path of movement of the actuating blocks 17c and 17a. At their respective extremes of travel, the actuating blocks 17c and 17d respectively contact right-angle shaped pivotally-mounted limit switch actuators 18c and 18d. The entire mechanism is adjusted so that the actuating block 170 effects the actuation of limit switch 18a to open same when tubular mast 13 reaches the maximum height permitted by the length of screw 14, while actuating block 170 effects the actuation of limit switch 18b to open'same when the tubular mast 13 is lowered to 4. the minimum height permitted by the actuating screw 14.

Referring now to FIG. 2, there is shown a preferred form of construction of the photocell unit 20 which is mounted on the top of the adjustable mast 1 0. Photocell unit 20 comprises a housing 23 having three vertical walls 23a and top and bottom walls 23b. An accordian-type dust shield 19 interconnects the bottom wall 23b and the top of housing 12. Mounting plate 230 is positioned in the housing 23 opposite its open vertical side and a plurality of laser beam responsive cells, here shown as three vertically aligned units 23d, are mounted in a suitable vertically spaced recess in the plate 23c. Such cells 23d may comprise any known device that will generate a voltage or change its electrical properties when a laser beam is incident thereon. Selenium or silicon photocell units are preferred. Thin horizontal light shields or spacers 23f are provided between the center photocell unit 23d and the two vertically adjacent cells.

Electrical leads 232 connect each of the photocells 23d to a suitable amplifying unit A (FIG. 6) which are preferably mounted in some protected location within the vehicle 2.

It is important that the total height of the central photocell unit 23d be at least equal to the minimum thickness or height of the laser beam 5 at all points within the effective working area traversed by the beam. This insures that at any time the optical center of this central photocell unit 23d departs from a position of exact vertical alignment with the center of the incident laser beam L, one or the other of the two vertically adjacent photocell units 23d will be energized to a greater or lesser extent. In other words, the vertical spacing between top and bottom photocell units 23d should not be greater than the minimum vertical thickness of the laser beam L at any point in the desired working area and the effective working heights of each of the top and bottom photocell units 23d should be at least 2 to 6 inches so that no normal changes in elevation of the vehicle 2 produced by the terrain will cause the photocell beam L to completely escape detection by the photocell unit 20 before correction of the mast height is initiated.

As previously indicated, the amplifying devices A (FIG. 6) are entirely conventional and translate the signals generated by each respective photocell unit 23d by any incident laser beam excitation into a usable electrical signal. The signal generated by the central photocell unit 23d and its associated amplifier A may be conveniently utilized to energize an indicating light 22 which is appropriately located within the vehicle 2 so that it is observable by the operator. So long as light 22 is energized, the operator is assured that at least a portion of the central photocell unit 23d is aligned with the laser beam L.

The amplified signals from the top and bottom photocell unit 23d are applied, through a manually-operable disconnect switch 23s, in opposingrelationship to a conventional reversible solenoid switch 21. Switch 21 comprises energizing coils 21a and 21b which are respectively energized in opposite directions by the amplifiers A connected to the top and bottom photocell units 23d. Whenever the current flowing in one of the coils is stronger than that flowing in the opposite coil. then the movable core 210 of the reversible solenoid 21 is shifted to effect a reversal of the polarity of the D. C.

electrical power source 24 that is connected to the mast adjusting motor 16.

i In the. neutral position of the reversible solenoid switch 21, the switch-actuating bar 21d is disposed in the solid line or neutral position N, wherein the power source 24 for reversible motor 16 is not connected to the motor. Let us assume that the vehicle 2 enters terrain that is slopingfldownwardly relative to the reference planedefined by the laser beam L. In that event, the upper photo cell unit 23d will be energized by the laser beam L and no energization willbe imposed on In the specific application of this invention to an automatic elevation recording device, as illustrated in FIG. 1, the flexible shaft 19 is connected to drive one component of a mechanical recorder 30, for example, the abscissa or vertical component. The horizontal component of motion is supplied to the recorder 30 by a speedometer cable 31 which is driven by a bicycle wheel 32 which is trailed behind the vehicle 2. Conventional gearing (not shown) is provided in between the bicycle wheel'32 and shaft 31 so that the rotation of flexible shaft 31 is exactly proportional to the distance travelled by the vehicle 2. Thus, the stylus (not shown) the lowerphotocell unit 23d. The differential solenoid will shift upwardly, moving the switch actuator 21b to the positionshown in dotted lines and labeled U, meaning that the D. C. source 24 will be connected to drive motor 16 in such a direction that the motor 16 will raise the mast to bring the center of the photocell unit 20 .into alignment with the center of the laser beam Such upward movement will continue until substantial'fequal ,energization. of the upper and lower photocell, units23d willbe produced which will effect the operation of the solenoid switch 21 to return it to its neutral position N, and the motor 16 will then be effectively deenergized. I

Referring particularly to FIGS. 5 and 6, the contacts of the limit switches 18a and18b'are illustrated in the circuit diagramras the switch elements'Ll and L2. It

will thereforebe apparent that the operation of either of the switches L1 or L2 to their open position will ef fectively stop the energization of the 'motor 16. In order that the motor 16 can thereafter be energized in the opposite direction, a pair of diodes D1 and D2 are'each connected across the contacts of the switches L1 and L2 in customary fashion. v i l Lastly, it is often desirable to provide} for manual operation of the reversible motor16 in order to initially position the mast 10 at an appropriate height to center the photocell unit'20 on the laserbeam L. Such manual operation may be effected byopening of switch 23s and manipulation of the manual switch MS, shown schematically' in FIG'. 6, between either of the dotted line positions. In the one position labeledD, the manual switch MS will effect the energization of the motor 16 to lower the mast. In the other position labeled U,

the motor 16 will be energized in the opposite direction to raise the mast. In either case, the mast height is manually controlled until the indicating light 22 is energized which tells the operator that the photocell unit 20 is then vertically aligned with the laser beam L.

In many applications of the signal-seeking, adjustable mast 10, it is desirable to derive a mechanical or electrical signal proportional to the height of the mast. Referring to FIG. 4, such mechanical signal may be conve- 'niently provided by mounting a pinion gear 14g on the of the recorder 30 will reproduce a trace which shows the elevation of the terrain traversed by the vehicle 2 as a function of the distance travelled by such vehicle.

From the foregoing description, it will be apparent to those skilled in the art that this invention provides a laser beam responsive signal-seeking, vertically adjustable mast which will automatically maintain a photocell unit on the mast in alignment with a laser beam. Other utilizations and modifications of this inventionwithin the scope of the appended claims will be readily apparem to those skilled in the art.

I claim:

1. A vertically adjustable mast for mounting a laser beam detecting unit comprising:

1. a mounting base having a horizontal 'wall and a depending peripheral flange defining a power transmission chamber; l

2. an upstanding cylindrical wall on said base;

3. a tubular housing anchored in said cylindrical wall;

- 4. a tubular mast slidablymounted in saidhousing, said mast having an internally threaded nut member rigidly mounted to the lower portion of said mast and concentrically disposed relative to the axis of said tubular mast; Y

5. an elongated screw engaging the threads of said nut member and having a lower shaft portion journalled in said horizontal wall andprojecting into said power transmission chamber; 6. a reversible motor mounted on said horizontal wall and having a vertical driveshaft projecting downwardly into said transmission chamber;

' 7. speed reduction means-interconnecting said motor shaft and said shaft portion of said screw, whereby said motor effects raising or loweringmovements of said mast relative to said housing; and

8. limit switch means mounted on the end of said shaft portion of said elongated screw and operably connected to said reversible motor to de-energize same whenever said mast approaches its top or bottom limiting position.

2. The combination defined in claim 1, plus an indicating shaft journalled in said base, and gear means for driving said indicating shaft in fixed ratio relationship with said elongated screw,.whereby the rotation of said indicating shaft is a linear function of the height of said mast.

' 3. The combination defined in claim 1, wherein said limit switch means comprises a horizontally disposed rod journalled in said transmission chambers reduction mum extension or maximum contraction of said mast. is :s s: 

1. A vertically adjustable mast for mountinG a laser beam detecting unit comprising:
 1. a mounting base having a horizontal wall and a depending peripheral flange defining a power transmission chamber;
 2. an upstanding cylindrical wall on said base;
 3. a tubular housing anchored in said cylindrical wall;
 4. a tubular mast slidably mounted in said housing, said mast having an internally threaded nut member rigidly mounted to the lower portion of said mast and concentrically disposed relative to the axis of said tubular mast;
 5. an elongated screw engaging the threads of said nut member and having a lower shaft portion journalled in said horizontal wall and projecting into said power transmission chamber;
 6. a reversible motor mounted on said horizontal wall and having a vertical driveshaft projecting downwardly into said transmission chamber;
 7. speed reduction means interconnecting said motor shaft and said shaft portion of said screw, whereby said motor effects raising or lowering movements of said mast relative to said housing; and
 8. limit switch means mounted on the end of said shaft portion of said elongated screw and operably connected to said reversible motor to de-energize same whenever said mast approaches its top or bottom limiting position.
 2. an upstanding cylindrical wall on said base;
 2. The combination defined in claim 1, plus an indicating shaft journalled in said base, and gear means for driving said indicating shaft in fixed ratio relationship with said elongated screw, whereby the rotation of said indicating shaft is a linear function of the height of said mast.
 3. The combination defined in claim 1, wherein said limit switch means comprises a horizontally disposed rod journalled in said transmission chamber''s reduction gearing, means interconnecting said lower end of said elongated screw and said rod, said rod having its opposed ends threaded, a pair of internally threaded blocks mounted on said threaded ends of said rod, whereby rotation of said rod effects axial movements of said blocks, and a pair of limit switches respectively actuated by said blocks when said blocks respectively move to positions respectively corresponding to maximum extension or maximum contraction of said mast.
 3. a tubular housing anchored in said cylindrical wall;
 4. a tubular mast slidably mounted in said housing, said mast having an internally threaded nut member rigidly mounted to the lower portion of said mast and concentrically disposed relative to the axis of said tubular mast;
 5. an elongated screw engaging the threads of said nut member and having a lower shaft portion journalled in said horizontal wall and projecting into said power transmission chamber;
 6. a reversible motor mounted on said horizontal wall and having a vertical driveshaft projecting downwardly into said transmission chamber;
 7. speed reduction means interconnecting said motor shaft and said shaft portion of said screw, whereby said motor effects raising or lowering movements of said mast relative to said housing; and
 8. limit switch means mounted on the end of said shaft portion of said elongated screw and operably connected to said reversible motor to de-energize same whenever said mast approaches its top or bottom limiting position. 